This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-094879, filed on Mar. 30, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a coating method and a coating apparatus each for applying an insulating material onto, for example, a substrate such as a semiconductor wafer or the like.
In a field of LSI, there has been a great demand for high-density mounting, and thus wiring conditions have become increasingly challenging. A higher wiring density leads to an increase in capacitance between wirings, manifesting a drop in signal transmitting speed. Delay in signal transmitting speed is proportional to the square root of the product of the wiring resistance and the electrostatic capacitance of the wiring, and the delay is a dominant factor in interfering with the rapid response of the entire device.
To avoid such delay, for example, it is conceivable to arrange properly the design of the wiring pattern or to increase the film thickness of a layer insulating film between wirings in different layers, but it is more typical to use a material with a small relative dielectric constant for a layer insulating film between wirings in the same layer.
However, such avoidance of the delay in signal transmitting speed only by selecting material has a limit, and thus proposal of a new avoiding technique is desired in consideration of progress still to come in high-density mounting.
An object of the present invention is to provide a new technology capable of further decreasing a relative dielectric constant of a layer insulating film.
To solve the aforesaid problems, the first aspect of the present invention is a coating method comprising the steps of: (a) applying an insulating film material onto a substrate; (b) foaming under a reduced pressure the insulating film material applied on the substrate; and (c) drying the insulating film material with the insulating film material foamed.
The second aspect of the present invention is a coating method comprising the steps of: (a) applying an insulating film material onto a substrate; and (b) drying the substrate coated with the insulating film material while ultrasound is supplied to the insulating film material applied on the substrate.
The third aspect of the present invention is a coating method comprising the steps of: (a) applying an insulating film material onto a substrate; (b) drying the substrate coated with the insulating film material to a degree at which fluidity of the insulating film material is kept to some extent while ultrasound is supplied to the insulating film material applied on the substrate; and (c) turning over and drying the substrate after the step (b).
The fourth aspect of the present invention is a coating apparatus comprising: a first processing chamber including a hold and rotation mechanism for rotating a substrate while holding it, and a supply mechanism for supplying an insulating film material onto the substrate held by the hold and rotation mechanism; a foaming mechanism for foaming under a reduced pressure the insulating film material supplied on the substrate; a second processing chamber for drying the insulating film material on the substrate; and a transport mechanism for transporting the substrate from the first processing chamber to the second processing chamber.
The fifth aspect of the present invention is a coating apparatus comprising: a first processing chamber including a hold and rotation mechanism for rotating a substrate while holding it, and a supply mechanism for supplying an insulating film material onto the substrate held by the hold and rotation mechanism; a second processing chamber for drying the substrate under a reduced pressure while ultrasound is supplied to the insulating film material on the substrate; and a transport mechanism for transporting the substrate from the first processing chamber to the second processing chamber.
In the present invention, vacuum bubbles remain in the insulating film, thereby decreasing the relative dielectric constant.
Additional Objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.